Sylvania



I(No Model.)

B. G. LAMME.

REGULATION 0F ROTARY TRANSFORMER DIRECT GURRBNT ELRGTROMOTIVR FORGE.

la? I4 W/TNESSES f /N VEN TOR NrTu T aTs aTnnT @Tirreno BENJAMIN- G. LAMME, OF vPITTSBURG, PENNSYLVANIA, ASSIGNOR TO TI'IE l IVES'IINGIICUSE ELECTRIC AND MANUFACTURING COMPANY, OAF PENN- SYLVANIA.

REGULATION F ROTARY-TRANSFORMER DIRECT-CURRENT ELECTRONIOTIVE FORCE.

SPECIFICATION forming part of Letters Patent No. 606,560, dated J une 28, 1898.

Application filed February 10,1898. Serial No. 669,847. (No model.)

T0 all whom t may concern.'

Be it known that I, BENJAMIN G. LAMME, a citizen of the United States, residing in Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in the Regulation of Rotarylransformer Direct-Current Electromotive Force, (Case No. 770,) of which the following is a specication. l

xo My invention relates to the transformation of alternating currents to'direct currents by means of rotary transformers and the variation of potential at the direct-current terminals of the rotary transformer.

The object of my invention is to provide a method and means whereby a wide variation of potential at the direct-current terminals of a rotary transformermay be secured and whereby the operation of direct-current mo- 2o tors at different speeds may be effected.

The system constituting my invention is particularly useful in connection with the utilization of alternatingr currents for electric railways, since it permits of the employment 2 5 of direct-current motors,which are more readily adapted to the great variations in speed necessary in such work, and since it provides means whereby the speed of'lsuch motors may be varied within any desired limits without variation of the resistance or circuit connections of such motors. My invention is, however, applicable and intended for use in connection with variable speed direct current motors irrespective of any specific applica- 3 5 tion of the power developed thereby.

In the accompanying drawings, Figure lis a diagram of apparatus and circuits suitable for practicing my invention, and Fig. 2 is a similar diagram of a slightly-modified con- 4o struction.

In Fig. 1, 1 is a two-phase alternating-current generator, and 2 and 2a are stationary transformers for kthe respective out-of-phase circuits, the secondary windings 3 and 3 of which are respectively provided with leads 5, (5, 7 and 8, and 5i, G, and S at intervals in order that a greater or less length of each secondary may be included in circuit, according to the electromotive force desired.`

9 is a rotary transformer provided with a 5o shunt eld-magnet winding 10.V

11 is a rheostat connected in series with the field-magnet winding 10 and provided /with means for including more or less of it in circuit, as may be desired.

12 and 12 are cholie-coils connected, respectively, in the circuits of the secondaries 3 and 3 of the stationarytransformers 2 and 2, which supply the rotary transformer i) with alternating current. The free end of 6o choke-coil 12 is provided with aswitcli-arm 13, by means of which any desired number of sections in theV secondary winding 3 may be includedin circuit with rotary transformer 9, and the free end of choke-coil 121L is pro- 65 vided with a similar switch-arm 13, which cooperates in the same manner with the secondary 3.

13 and-14 are direct-current motors connected across the circuit supplied by the di- 7o rect-current end of the rotary transformer 9.

If the motors are to be used for propelling a railway-vehicle, means may obviously be provided, if desired,wh'ereby they may be connected either in series or in parallel, such construction andarrangement being wellunder- .stood in the art.

For convenience of illustration I have shown a single-phase circuit in Fig. 2; but it`will be understood that the invention is not limited 8o in any case as regards the number of phases of current. The apparatus and circuits illustrated in Fig. 2 also differ from what is illustrated in Fig. 1 as regards the number and arrangement of the choke-coils. It will be seen that in Fig. 2 I employ a series of chokecoils 12, 12, 12b, and 12C, one for each division of the secondary winding, in lieu of the single coil of Fig. l. Either arrangement is suitable for practical use; but inasmuch as 9o the electromotive force and the torque vary with the length of transformer secondary included in circuit it mayin some cases bedesirable to employ a series 'of choke-coils of 5 different capacity, as is indicated in Fig. 2. 95

The system is operated as follows: Assuming that a slow speed for the motors 13 and 14 is desired, if the rheostat 11 and the switch arm 123 or the switch-arms 13 and 13, as the case maybe, be in the position shown it is obvious that the transformer 2 will be supplyingits lowest electromotive `force and the field of the rotary transformer will be as weak as it is possible to make it with the apparatus shown. lVith this arrangement of parts the lagging eurrentin the alternating-current circuit will generate in the choke-coils counter electromotiye forces, which lower the alternating-current electromotive force of the rotary transformer, and thus lower the directcurrent electromotivc force to the minimum point.

ln order to increase the direct-current electromotive force, and consequently the speed of; the direct-current motors, the Yfieltl-inzmnet of the rotary transformer may be gradually strengthened by cutting` out step bys'tep the resistance of the rheoslat ll until the field is strong enough to produce a current in the alternating-currcnt circuit that leads the electromotive force, in which condition a component of the eleetromotive fore-e generated in the choke-coil will be added to that supplied by the length of transformer secondary included in the circuit, so that the electromotive force supplied bythe rotary transformer is higher than that supplied by the stationary transformer. lf a still greater speed of motors desired, another length ol' the stationary transformer may be included in circuit and the entire resistance of the rheostat simultaneously inserted in the field-circuit of the machine, after which the operation above described may be repeated. This operation may be continued until the entire secondary of the transformer is included in circuit and all of the resistance is eut out of the rotarytransformer field-circuit,when the maximum direct-current electromotive force, and consequently the maximum speed of the motors, will be obtained.

lu order to decrease the speed of the motors, the operations above described will obviously be reversed.

It will be understood that by this method a very wide range of electromotive force, and consequently a very wide range of speed of the motors, may be obtained without the use of a regulating-rheostat in the circuit oi' the motors.

lt will also be understood that the invention is not limited to the specific type of rotary-'lield-magnet winding shown nor to the specific means of Varying' the potential at the terminals of the secondary of the stationary transformer. lt will be further understood that any suitable mechanical devices Afor operating; the switches utiliz/.ed in the system may be employed.

l claim as my inventionl. ln a system of electrical distribution, the combination with a stationary transformer havingmeans for varying the electr-emotivo Yforce supplied by its secondary, of a rotary transformer receivingourrent :from said transformer secondary, one or more ehehe-coils, means for connecting;l the same in said sec ondary circuit and means for varying;` the field-magnet excitation of the rotary transformer, whereby a Wide variation of potential at the direct-current terminals may be cured.

2. In a system of electrical distrilnition, the combination with a stationary transformer having means for varying the electromotive force supplied by its secondary, of a rotary transformer receiving' current from said transformer secondary, one or more direct-current motors receiving current :from said rotary transformer, one or more choke-coils, means for including the same in the alternating current circuit and means for "varying the `Held-magnet excitation oi' the rotary transformer whereby the speed of the dircct-current motor or motors maybe varied within wide limits.

ln asystem of electrical distribution, the combination with a stationary transformer provided with means for varying t-he active length of its secondary winding, of a rotaryv transformer, one er more direot-currcnt motors, a choke-coil arranged to be connected with any aotivelength of the stationary transformer secondary and means for varying the excita-tion of the rotary-transformer licht magnet, substantially as and for the purpose set forth.

ln testimony whereof l have hereunto subscribed my name this Sth day of February, A. D. i803.

BENJ. tt. Tlalrthl lil.

ilfitnesses: Y

Wirsinuv et. @ama ll'. tl. Tuner..

lOO 

